Oscillating Table

ABSTRACT

Oscillating table in which the oscillation drive, comprising a hydraulic actuator, transmits the oscillating motion to the mould via a spring subject to bending stress, for example a fitted rod. The body of the hydraulic actuator is also anchored to the floor by means of a fitted spring subjected to bending stress. Thus thanks to the absence of any mechanical bearings in the drive mechanism, all disadvantageous movements caused as a result of bearing play, which increases at high oscillation frequencies, are eliminated. Moreover, the use of mould guide elements having a much simpler design and consisting of straightforward bars, also ensures greater guidance precision and enables a reduction in the oscillation marks on the cast product, a reduction that is even more noticeable when working at higher oscillation frequencies. Advantageously, the presence of an anti-roll device, consisting of two or more pairs of bars, for example two pairs, ensures good torsional rigidity of the table.

FIELD OF THE INVENTION

This invention relates to an oscillating table, in particular to atable, used for instance in bloom and billet production plants, used toobtain the oscillation of the mould.

PRIOR ART

Conventional oscillating tables are described in various patentdocuments. One such document, U.S. Pat. No. 4,456,052, describes acontinuous casting apparatus in which a casting mould, mounted in asuitable mounting arrangement, is oscillated by means of oscillationlevers. These levers are hinged at one end to the mould mountingarrangement and at the other end to a supporting block. The presence ofbearings, and other mechanical parts that are subject to wear, meansthat the use of such devices is disadvantageous, as they require a greatdeal of maintenance which is expensive in terms of money and time.Moreover, during the production process some disadvantageous movementsof the oscillating table occur as a result of bearing backlash, whichincreases at higher oscillation frequencies. Some of these drawbackshave been overcome by means of new oscillating systems based on the useof leaf springs.

A document, DE2248066, describes a device in which a mould is guidedlaterally by two leaf spring assemblies arranged parallel to one anotherand one above the other. Oscillation is brought about by a hydrauliccylinder. The two spring assemblies, which are arranged one on each sideof the mould and clamped in place on one side to the bearing structureand on the other side to the mould, must absorb all the guide forces.The springs are, in actual fact, subjected to tensile as well as axialand bending stresses. On account of this the spring assemblies must bemuch longer and much thicker than is necessary for the maximum tensileforces that occur. Due to the large size of the spring assemblies,higher drive forces are necessary, that is to say the oscillation drivemust be correspondingly larger in size. Moreover, the service life ofthe spring assemblies is reduced because of the high alternating bendingstress occurring due to the large thickness. The use of very long springassemblies means that there is also a more pronounced elastic behaviour,resulting in greater deflections and deviations of the mould from thedesired guide path. Thermal influences are also more noticeable.

Another document, WO9912676, describes a device in which a mould issupported on a mould-supporting device by means of at least one pair ofleaf springs, extending approximately transversely to the direction ofoscillation and absorbing forces in the elastic range. At least onefirst guide element extends from the mould-supporting device towards themould in a first direction and at least one second guide element extendsfrom the mould-supporting device towards the mould in a directionopposite to the first direction. The leaf springs are arranged in such away that they are bend-resistant in the directions transverse to thedirection of oscillation and bendable in the direction of oscillation,and are only subjected to tensile forces. Said device is thus certainlymore compact that those described previously but still has severaldrawbacks: the use of leaf springs does not enable high precisionguidance or the reduction of oscillation marks on the cast product; theoscillating table has poor torsional rigidity; its operation requiresthe use of mechanical bearings with the drawbacks described above;finally, the oscillation frequency is not easily increased.

This invention aims to overcome these drawbacks.

SUMMARY OF THE INVENTION

One of the main purposes of this invention is to provide an oscillatingtable that is of a more straightforward design and more compact and thatallows greater precision in the guidance of the mould even if thefrequency of oscillation is increased. Another purpose is to produce anoscillating table in which there are no mechanical parts subject towear, to enable a significant reduction in the amount of maintenancerequired and thus obtain considerable savings in terms of time andmoney.

This invention therefore aims to overcome the drawbacks described abovewith an oscillating table having the characteristics set forth in claim1.

The total absence of bearings in the oscillating table according to thisinvention not only means that the table is maintenance-free but alsoenables the elimination of all disadvantageous movements caused as aresult of bearing clearance, which increases at high oscillationfrequencies.

The oscillation drive mechanism, comprising a hydraulic actuator,advantageously transmits the motion via a spring subjected to bendingstress, for example a fitted rod.

According to one advantageous alternative form of this invention, thebody of the hydraulic actuator is also anchored to the floor by means ofa fitted spring subjected to bending stress. Thus also the drivemechanism has no mechanical bearings, with the advantages describedabove.

Furthermore, the use of simpler guide elements, that no longer consistof leaf springs comprising a plurality of elements that are joined toone another, but of straightforward bars, ensures greater guidanceprecision and enables a reduction in the oscillation marks on the castproduct, a reduction that is even more noticeable when working at higheroscillation frequencies.

Said guide elements also have a long service life and automaticallycompensate thermal expansions thus avoiding guide deviations.

Finally, the presence of an anti-roll device, comprising two or morepairs of bars, for example two pairs, ensures good torsional rigidity ofthe table. Each bar in each pair has a first end that is fastened to themobile part of the table and a second end that is fastened to the fixedpart, in opposite order in relation to the corresponding ends of theadjacent bar of the same pair. According to the direction of thetorsional moment, in the case of two pairs of bars, two bars will besubjected to tensile stress, acting as tension bars, while the other twowill be subjected to compressive stress, acting as compression members.

The dependent claims describe preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of this invention will becomeclear from the following detailed description of a preferred, but notexclusive, embodiment of an oscillating table that is merelyillustrative and not limitative, with the help of the drawings that areattached hereto, in which:

FIG. 1 is a vertical cross-section of the oscillating table according tothis invention;

FIG. 1 a is a large view of a component of the oscillating table of FIG.1;

FIG. 2 is a cross-section of the plan view of the oscillating table inFIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

With reference to FIG. 1, an oscillating table is illustrated with anexternal supporting structure 1, that is fixed to the floor.

In one particularly advantageous alternative embodiment, said structurecomprises a single beam that supports the structure on the floor andthat in turn comprises all the necessary elements in order to supportthe various parts that make up the table.

A mould 3 comprising a cylindrical crystallizer 2 is mounted in theexternal supporting structure. The oscillating movement of said mould iscontrolled by an oscillation drive mechanism, comprising a hydraulicactuator 4, via a spring subjected to bending stress 5, for example afitted rod. Said spring subjected to bending stress 5, is connected atthe other end to an element 8, for example a bar or a monolithic beam,integral with the mould 3.

According to one advantageous alternative embodiment the body of theactuator 4 is also anchored to the floor by means of a spring subjectedto bending stress 9, for example a fitted rod. Since there are nomechanical bearings whatsoever in the above-described oscillation drive,all the backlash, characteristic of said components, which arenotoriously subject to wear, is eliminated.

There are elastic guide elements 6, 7 to prevent any deviation of themould 3 from the predetermined path. Said elements 6, 7, which areoblong in shape, are oriented approximately on radial lines of the arcdefined by the cavity of the crystallizer 2 if said cavity iscurvilinear; on basically parallel lines if the cavity of thecrystallizer is rectilinear.

In this embodiment of the invention said elastic guide elementsadvantageously consist of a first pair of upper bars 6 and a second pairof lower bars 7, both pairs having a flat cross-section. The elasticbars 6, 7 must absorb tensile forces only and are therefore arranged soas to be bend-resistant in the directions transversal to the directionof oscillation and bendable in the direction of oscillation. The fourbars 6, 7 are fastened to one end of the mould 3, i.e. to the mobilepart of the table, by means of fastening devices 10, for example bolts,and at the other end to the external supporting structure 1 by means offastening devices 11.

One alternative embodiment provides for the use of leaf springs orsprings of a similar type as the elastic elements to guide the mould 3.

To contrast the torsional moment that occurs on a plane that isbasically orthogonal to the casting direction, the table according tothis invention advantageously incorporates an anti-roll device,comprising two or more pairs of bars 12. Said bars 12, which arehorizontal and arranged in directions that are basically transversal tothe elastic guide elements 6, 7, ensure a predetermined torsionalrigidity of the table. Each bar in each pair has a first end that isfastened to the mobile part of the table and a second end that isfastened to the fixed part, in opposite order in relation to thecorresponding ends of the adjacent bar of the same pair. According tothe direction of the torsional moment, in the case of two pairs of bars,two bars will be subjected to tension, acting as tie rods, while theother two will be subjected to compression, acting as struts.

In another advantageous alternative embodiment there are elastic means13, for example compression or air or leaf springs, the function ofwhich is to lighten the mould 3 and the actual table structure ensuringa better distribution of the weight. Thanks to the total absence ofmechanical bearings in the oscillating table according to this inventionthe table requires no special maintenance, resulting in savings in termsof time and money, and all disadvantageous movements due to bearingplay, which increases at higher oscillation frequencies, are eliminated.Moreover, the use of much simplified elastic guide elements ensuresbetter precision in mould guidance and results in a reduction in theoscillation marks on the cast product.

Finally, thanks to the improvements described above, the oscillatingtable according to this invention is more compact and of a simplerdesign and can be used at oscillation frequencies of above 4.5 Hz, whichis higher than the normal frequencies of 3.5 Hz.

The specific embodiments described in this document are not limitativeand this patent application covers all the alternative embodiments ofthe invention as set forth in the claims.

1. Oscillating table comprising a mobile structure, mounted in asupporting structure integral with the floor, wherein the mobilestructure comprises a mould (3) defining a first casting direction andbeing guided in an oscillation by first elastic members (6, 7) having anelongated shape and arranged transversely to the direction of casting, ahydraulic actuator (4) transmitting oscillations to the mould (3),characterized in that there are provided two or more pairs of bars (12),arranged horizontally in a second direction basically transversal to thefirst elastic members (6, 7) and to the first direction of casting,whereby the table is provided with a predetermined torsional rigidityabout an axis substantially parallel to the first elastic means. 2.Oscillating table according to claim 1, wherein each bar (12) of eachpair has a first end fastened to the mobile structure and a second endfastened to the supporting structure, in opposite order with respect tothe corresponding ends of the other bar in the pair.
 3. Oscillatingtable according to claim 1, wherein there are provided second elasticmembers (13) connecting the mould (3) to the supporting structure thatlighten the mould (3) and distribute its weight in a uniform manner. 4.Oscillating table according to claim 3, wherein there is provided athird elastic member (5) clamped in place and connecting the hydraulicactuator (4) to the mould (3).
 5. Oscillating table according to claim4, wherein there is a fourth elastic member (9) clamped in place andconnecting the hydraulic actuator (4) to the floor.
 6. Oscillating tableaccording to claim 5, wherein said third and fourth elastic members (5,9) consist of a spring subjected to bending stress.
 7. Oscillating tableaccording to claim 6, wherein said spring subjected to bending stressconsists of a fitted rod.
 8. Oscillating table according to claim 3,wherein said second elastic members (13) consist of compression or airor leaf springs.
 9. Oscillating table according to claim 1, wherein saidfirst elastic members (6, 7) consist of bars or leaf springs.